Painting a wooden fireplace is similar to painting brick or concrete fireplaces. The only difference is painting wood usually requires fewer steps. Most wooden fireplaces have been painted or stained in the past, so the most challenging part may be preparing the surface to accept new paint. For a long-lasting paint job, you don't need to strip all the old fireplace paint, but you do need to spend some time sanding it down. An electric sander can make short work of the sanding process. They're fairly inexpensive and worth investing in for large fireplace painting projects.
Remove any existing chipped or flaking paint, using the scraper and wire brush. You don't have to scrape down to the wood, just remove any loose paint.
Sand the surface with an electric sander or by hand with sandpaper. Rough up the surface so it'll accept new paint. If the wooden fireplace was stained, sand off glossy surface coatings or the paint won't adhere.
Vacuum the area to remove any paint chips and dust. Dust can mix in with the paint and create a grainy finish.
Prime the wood if it's a new fireplace and has never been painted. This is generally only necessary for virgin wood, but a coat of good-quality primer can help the paint last longer on any surface.
Apply two thin coats of your chosen interior latex paint, using a paintbrush. Avoid applying one thick coat as it'll take much longer to cure and won't adhere as well to the fireplace. Two thin coats bond together and last longer. Allow to dry between coats.
If you're going from a dark paint or stain to a lighter colour, a coat of primer will provide a neutral base to paint on. This will provide truer paint colour in fewer coats.
Some areas may have building codes regarding types of paint that can be used on wooden fireplaces. Check with your local building codes office if there's any question.